Mobile phones, personal digital assistants (“PDAs”), digital cameras, MP3 players, and other electronic devices utilize light-emitting diodes (“LEDs”), organic light-emitting diodes (“OLEDs”), polymer light-emitting diodes (“PLEDs”), and other solid-state transducer devices for backlighting. Solid-state transducer devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination. FIG. 1A is a cross-sectional view of a conventional LED device 10a with lateral contacts. As shown in FIG. 1A, the LED device 10a includes a substrate 20 carrying an LED structure 11 having an active region 14, e.g., containing gallium nitride/indium gallium nitride (GaN/InGaN) multiple quantum wells (“MQWs”), positioned between N-type GaN 15 and P-type GaN 16. The LED device 10a also includes a first contact 17 on the P-type GaN 16 and a second contact 19 on the N-type GaN 15. The first contact 17 typically includes a transparent and conductive material (e.g., indium tin oxide (“ITO”)) to allow light to escape from the LED structure 11.
FIG. 1B is a cross-sectional view of another conventional LED device 10b in which the first and second contacts 17 and 19 are opposite each other, e.g., in a vertical rather than lateral configuration. During formation of the LED device 10b, the N-type GaN 15, the active region 14 and the P-type GaN 16 are stacked sequentially on a growth substrate (not shown), similar to the substrate 20 shown in FIG. 1A. The first contact 17 is formed on the P-type GaN 16, and a carrier substrate 21 is attached to the first contact 17. The growth substrate is then removed and the second contact 19 is formed on the N-type GaN 15. The structure is then inverted to produce the orientation shown in FIG. 1B. A converter material 23 and an encapsulant 25 can then be positioned over one another on the LED structure 11. In operation, the LED structure 11 can emit a first emission (e.g., blue light) that stimulates the converter material 23 (e.g., phosphor) to emit a second emission (e.g., yellow light). The combination of the first and second emissions can generate a desired color of light (e.g., white light).
The vertical LED device 10b has enhanced current spreading, light extraction, thermal properties, and accordingly a higher efficiency than the lateral LED device 10a of FIG. 1A. However, despite improved thermal properties, the LED device 10b still produces a significant amount of heat such that the differences between the coefficients of thermal expansion of the LED structure 11 and the underlying carrier substrate 21 can cause delamination between the two components and/or other damage to the packaged device. Additionally, as shown in FIG. 1B, the vertical LED device 10b requires access to both sides of the die to form electrical connections with the first and second contacts 17 and 19, and typically includes at least one wirebond coupled to the second contact 19. Wirebond connections take up more space and require more intricate formation techniques than other electrical coupling methods (e.g., solder reflow processes), and therefore may be ill-suited for applications with tight die spacing. Moreover, various portions of the LED device 10b (e.g., the converter material 23, the encapsulant 25) are formed after singulation at a die level (FIG. 1B), and thus require precise handing that further increases manufacture time and cost. Accordingly, there remains a need for vertical LEDs and other solid-state devices that facilitate packaging and have improved the performance and reliability.